The present invention relates generally to digital multimeters. More particularly, the invention relates to a digital multimeter having an improved arrangement for sealing predetermined portions of the housing.
Digital multimeters (DMMs) function to measure a number of parameters generally needed for service, troubleshooting and maintenance. Such parameters may include AC voltage and current, DC voltage and current, resistance and continuity. In some cases, a DMM may measure other parameters such as capacitance and temperature.
A DMM will often be configured as a hand-held unit having a rotary selector knob by which various functions are selected. A plurality of lead jacks are provided in the case (i.e., housing) of the unit for connection of test leads. The specific jack used may depend on the function that has been selected. An LCD display provides a reading of the tested parameter.
The traditional DMM housing has top and bottom case halves which are joined together to define an interior cavity. At least one of the case halves is typically formed of a rigid polymeric material overmolded with a softer polymeric material to provide a gripping surface. Sometimes, the softer polymeric material has been formed to define a “rib” extending around the periphery of one case half. When the two case halves are brought together, this rib comes into contact with a rigid surface on the other case half, causing the rib to deform, or “crush.” Often, this type of crushed rib arrangement has provided an effective environmental seal for the multimeter housing. In some applications, however, a crushed rib type of seal might be less effective.
Details regarding the construction and operation of multimeters may be discerned from U.S. Pat. Nos. 7,034,517, 6,466,003 and 6,043,640, incorporated herein by reference.